For many years, since the development of outdoor grilling appliances in the nineteen forties and fifties, there has been a desire for an effective electrically powered outdoor cooking appliance. It has long been believed that such a device might be made more convenient and easier to use, e.g., without requiring a special fuel like charcoal or propane. In recent years, the growing availability of electrical energy from renewable or otherwise environmentally friendly resources has added further impetus for the use of such electrical appliances.
The current electrical outdoor grilling appliance art includes various types of products. In a first type, an electrical resistance heating element is embedded in a cooking grate. As the current heats the electrical element, the electrical element transfers heat by conduction to the grate, which is usually made of a conductive material such as aluminum. The grate, in turn, heats the food by conduction. Typically, open slots are provided in the grate for draining grease. By alternating the contact areas and the open slots of the grate, the grill can produce, under favorable circumstances, a pattern of “sear” marks, which are desirable when grilling.
However, this first type of electric grill suffers from the problem that the temperature of the heated cooking surface must be held below the ignition point of the grease so that fire will not occur at the point of cooking. However, the required low temperature will not sufficiently vaporize the grease to produce the smoke necessary for flavoring the meat when grilling. Furthermore, the required low temperature allows accumulated grease to gather on the surface of the cooking grate around the food, despite the provision of grease drainage features.
In a second type of electric grill, a radiant heating element is suspended below an open wire-type cooking grate and is surrounded by an insulating material. Food is cooked by radiant heat through the open grate and by some conduction from the cooking grate, which is heated by the radiant element. The conductive heat from the grate can produce, under favorable circumstances, a pattern of “sear” marks desired for grilling. This type of grill is generally described in U.S. Pat. No. 6,104,004.
Unfortunately, in this second type of electric grill, good cooking performance can only be achieved by cooking with the lid closed as much as possible. The design and cooking performance of the grill depend upon the establishment of a large radiant cavity below and above the cooking grate. If the lid is open, the cavity is not only split into two open halves, but most of the radiant energy generated by the heating element is lost to the atmosphere with little effective retention by the food or by the open wire cooking grate.
In a third type of electric grill, a radiant element is used to heat a specific type of grate. The grate (a) restricts convective heat, (b) delivers predominately infrared heat to the food supported on it, and (b) uses conductive heat to create a pattern of sear marks on the food. In this configuration, a single or double conical heat shield is placed below the heating element to minimize heat loss. This type of grill is generally described in U.S. Pat. No. 8,399,810.
However, this third type of grill, though presenting better performance, takes a long time to warm up to a sufficient operating temperature for prompt searing. In addition, in grills of both the second type and the third type described above, a significant amount of free convective flow continuously occurs past the radiant heating element, thus having the effect of cooling the radiant element.
In addition, each of the prior art electric grills described above also suffers from a lack of power density. This condition is driven by the wattage limitations of standard US residential electrical systems. A standard 120 volt current, as limited by a 15 amp circuit breaker, provides an absolute upper power limit of only 1800 watts.
This power limit produces a thermal energy equivalent of just 6,147 BTU/hr for an entire cooking surface. Consequently, in the case of a 200 square inch cooking surface, the maximum power density available is only 30.7 BTU/hr/in2. This power density is much lower than the 100 BTU/hr/in2 maximum provided by a typical gas grill and is also much lower than the 60 to 80 BTU/hr/in2 maximum provided by some newer gas infrared cooking systems. As a result, in less than ideal conditions, such as a cold windy day, the electrical cooking appliance may not produce adequate cooking results.